Italian police have seized a large drugs haul in a southern Italian port as part of a massive global operation against drug-smuggling.

Thousands of kilogrammes of cocaine were found hidden in a marble shipment in Gioa Tauro, Calabria, police said.

About 100 people were also reportedly arrested in Italy, along with about 30 in Colombia and 17 in Australia, France, the Netherlands and Spain.

Officers from three continents were involved in the three-year operation.

'Mafia' links

Italian police said the operation was run by a local Mafia organisation known as the 'ndrangheta.

The main significance is the fact that, internationally, law enforcement agencies from six other countries were able to come together and work as a team

Australian federal police inspector Peter Duffy

More than five tonnes of cocaine have reportedly been found in the course of the investigation - in which more than 1,000 Italian police were also involved.

Police said one of the largest hauls was uncovered when they found hundreds of kilogrammes of cocaine stashed inside a consignment of marble blocks hidden in shipping containers in a ship in the southern Calabrian port of Gioa Tauro.

He also praised the collaboration between Italian authorities and global police authorities "that allowed such a major, international anti-drug and anti-terrorist operation".

Australian federal police inspector Peter Duffy said the partnership between all the countries was crucial to smashing the drugs ring.

"The main significance is the fact that, internationally, law enforcement agencies from six other countries were able to come together and work as a team and in partnership in order to dismantle an organised crime organisation," he told Reuters.

The drugs, from Colombia and Venezuela, were allegedly smuggled to Europe and Australia. Police said African states such as Togo were often used as transit points.

Anti-Mafia prosecutor Pierluigi Vigna said that cocaine had surpassed heroin as drug of choice for smugglers.

It is thought that some of the profits from the operation were being used to fund paramilitary groups in Colombia.